Process for the preparation of 2, 3-, 2, 4-, and 2, 5-dichlorostyrene



ni cd S s. 2,979,536

PROCESS FOR THE PREPARATION OF '2,3-, 2,4-,

- AND 2,5-DICHLOROSTYRENE Frederick J. Soderquist, Essexville, and James L. Amos,

Midland, Mich., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Filed June 26, 1957, Ser. No. 668,026

6 Claims. (Cl. 260-650) V This invention concerns the preparation of 2,3-, 2,4-, and 2,5-dichlorostyrene. a process wherein 2,3-, 2,4-, and 2,5-dichloroisopropylbenzene, hereinafter referred to as an isomeric dichloro The process of this ren' -O i More particularly, it concerns least one of the isomeric dichlorocumenes having one 77 chloro substituent ortho to the isopropyl substituent, advantageously in admixture with an inert diluent gas such as steam, nitrogen, carbon dioxide, non-reactive hydrocarbons such as methane, vaporized benzene, unconverted dichlorocumenes themselves and the like over a demethanating catalyst at a reaction temperature between 525 and 750 C. and preferably between 600 and 700 C., cooling the efiiuent gases to condense liquid product, and fractionating, preferably under vacuum, to obtain the desired dichlorostyrene product. In its other aspect, the demethanating reaction of this invention can be carried out at similar temperatures in the absence of catalyst.

Operable =dichlorocumenes include the 2,3-, 2,4-, and 2,5-dichlorocumenes and mixtures thereof.

' Demethanating catalysts which are advantageously used include (1) the activated or calcined aluminas, including the activated bauxites, and (2) chromic oxide and mixtures thereof with ferric oxide.

f The proportion of diluent to feed stock when added diluent is used can be varied widely, advantageously between 0.02 and 10 parts by weight of diluent per part of feed stock. A proportion of 3 parts by weight of diluent per part of feed stock is preferred.

A space velocity between 5 and 100 grams of oil feed per 80 mls. of catalyst (or per 80 mls. of cracking zone when no catalyst is used) per hour can advantageously be'used. However, a space velocity of 20 g. of oil feed per 80 mls. of catalyst per hour is preferred.

In practice, a feed stock of one or more of the indicated dichlorocumenes advantageously together with added diluent is passed through a reaction zone maintained at a reaction temperature between 525 and 750 C. at a space velocity between Sand 100, as indicated. Efiluent from the reaction vzone is cooled to condense liquid product. Water is separated therefrom when steam is used as diluent. The liquid product is then fractionated to separate the desired dichlorocumenes.

The following examples show ways in which the invention has been practiced.

EXAMPLE I.--PREPARATION OF 2,3-DICHLORO- STYRENE FROM 2,3-DICHLOROCUMENE A quantity of 699 g. of 2,3-dichlorocumene of 98.3 percent purity at a rateof 19.4 g. per hour and 2249 g. of steam at a rate of 6 2.5 g. per hour was passed over mls. of an activated alumina catalyst promoted with ferric oxide.- A continuous operation was conducted for- 36 hours during which time the catalyst temperature was gradually raised from 600 to 690 C. A quantity of 632 g. of liquid product was recovered by cooling the efiluent gases and separating and discarding condensed water. The liquid product was distilled and analyzed by infra-red spectrometry. The product contained the .following:

Percent by weight Benzene Toluene Xylenes Dichlorobenzenes Styrene Isopropylbenzene a-Methylstyrene 0.03 2,3-dichlorostyrene 9.50 2,3-dichloroisopropylbenzene 86.00 2,3-dichloroisopropenylbenzene 0.00 Unidentified higher boilers Calculations based on the above run indicate 8.2 percent conversion to 2,3 -dichlorostyrene and 25.9 percent yield based on 2,3-dichlorocumene consumed. Unconverted feed can be recycled.

EXAMPLE II. PREPARATION OF MIXED DI- CHLOROSTYRENES FROM MIXED DICHLORO- CUMENES A quantity of 1117 grams of dichlorocumenes having an isomer distribution of 16 percent 2,3-dichlorocumene,

Dichlorocumenes 50.6 3,4-dichloroisopropenylbenzene 3.9 Undetermined and higher boilers 7.0

Based on 'the above data, the following conversions and yields were calculated, based on an 83.7 percent recovery:

Percent conversion to 2,3-, 2,4-, and 2,5-dichlorostyrene 24.7 Percent yield to 2,3-, 2,4-, and 2,5-dichlorostyrene 41.5 Percent conversion to 3,4-dichloroisopropenylbenzene 3.1 Percent yield to 3,4-dichloroisopropenylbenzene 5.2

In contrast thereto, 735 g. of a dichlorocumene isomer mixture consisting essentially of percent 3,4-dichlorocumene and 14 percent 2,3-dichlorocumene was passed together with 2405 g. of steam over 80 mls. of

70 an activated alumina catalyst promoted with ferric oxide at rates of 19.4 g. and 63.3 g. per hour, respectively. Total time was 38 hours, during which time the catalyst 2,979,536 Pat n d. Av 1. .96.1...

0.6 Dichlorostyrenes 28.2

temperature was gradually raised from 600 to 700 C. A quantity of 700 g. of liquid hydrocarbon product was recovered having the following analysis:

Percent by weight Based on the above recoveries, the following conversion and yield data were adduced:

milliliters of cracking zone per hour, whereby demethanation of the isopropyl group predominates to the substantial exclusion of dehydrogenation, and recovering a dichlorostyrene product therefrom.

2. The method of claim 1 wherein the demethanating zone temperature is varied between 600 and 700 C.

3. The method of claim 1 wherein an inert diluent gas is added to the feed stock in amount ranging between 0.02k and weight parts of diluent per part of feed stoc 4. The method of claim 1 wherein the demethanating zone contains a demethanating catalyst of the group consisting of activated aluminas, activated bauxites, chromic oxide, and mixtures of chromic oxide with Percent conversion to 2,3-dichlorostyrene 8.0 fem: oxlde- Percent; yield to 2,3-dic1'fl0rostyrene 17 3 The method f claim 1 wherein the space velocity Percent conversion to 3,4-dichloroisopropenylben- 1S grams of feed Stock P 80 mlllllltefs of cracklng Zens 3L6 zone per hour. Percent yield to 3,4-dichloroisopropenylbenzene 68.4 20 A met od for the preparation of a dichlorostyrene It is apparent from the foregoing examples that dichloroifi g suiistltuent .ortho Vmyl g styrenes having one chloro substituent ortho to the isome O compf'lses passmg at one F propyl substituent can be demethanated 'to the corre- 0f the $0111? coPsstmg P and spending dichlorostyrenes pursuant to the process of this admlxture Wlth steam dlluef'lt, the P p invention, whereas other dichlorocumenes are largely deby vilelght' of steam to feed Stock being 3 l, hydrogenated to the corresponding dichloroisopropenyla fiemetllanamlg calalltsi of the g p consllstmg P benzenes under otherwise similar reaction conditions. actlvated 811111111185, activated bfluXlteS, om c mode The following table summarizes results obtained with and mlxtures of chromic oxide with ferric oxide mainvarious feed stocks, catalysts, diluents, and reaction temtamed at a temperature between 600 and 700 C. and peratures, pursuant to the process of this invention. a 1 veloclty 0f 20 grams of feed Stock P All runs were made at a space velocity of 20 grams of m1ll1l1ters of catalyst per hour, whereby demethanation oil feed per 80 mls. of catalyst or cracking zone per of the lsopropyl group predominates to the substantial hour. exclusion of dehydrogenation, cooling the efiiuent gases Tabl I DICHLOROSTYRENES FROM DICHLOROCUMENES Crude Product Analysis Steam Temp t ir i Wu P tP t? t P t P t F C I R 1.. 0C lme, QYCGH ercen (TCQH ercen GICEH eed Stock am yst a Ratio Hours DCJS DOC2 DOIPeB Mate- Conv. Yield Conv. to Yield rial Reto Dos DCIPeB DCIPeB covery DCS 3,4-DCO Act.Al:Oa+Fez03 550-040 3.11 127 0.14' 09.9 25.4 89.3 o 0 22.9 00.9

AchAlzO -l-FeaOa -L 005-700 291 33 14.7 57.9 0.1 02.5 13.2 25.3 5.1 9.8

10% 2,3-Doo-.--. %3 6 Wi None "005-700 0.0:1- as 10.3 07.9 2.0 90.8 10.2 20.0 1.3 4.0 10%a,4-'Doo 10% 2.3-DCO AcihAltoa-i-Fezos 025-700 301 12 19.2 45.8 8.0 71.7 15.0 22.3 5.8 0.0 10% 3.4 1300"--. 2 }A0t.m,03- -Fez05 000-700 3.111 as 0.7 49.0 28.8 90.7 0.0 12.0 20.4 48.0

0 7 fig }None 000-700 am as 10.0 70.7 0.4 94.9 10.4 34.0 0.1 20.0

0 u. Nitrogen Diluent 10% 23-1500... Aet.Al1O +FezO3.-.-- 000-590 1:1N2 43 10.0 50.9 0.0 87.3 15.8 28.5 5.3 9.0 10% 9,4 Doo 35 I 10% 2,3-DGO 68% and None 000-700 mm 45 15.0 50.0 2.0 94.4 10.1 34.0 2.5 5,3 10% a,1-'Doo X DOS =Dichlorostyreue. 2 D00 Diehloroeurnene. 2 D CIPeB Diehloro soprepenylbenzene.

to condense liquid product, separating water therefrom, 5 and fractionating said liquid product to separate .and

recover a dichl-orostyrene product.

References Cited in the file of this patent UNITED STATES PATENTS .Dreisbach Mar. 8, 1938 Amos et a1. Nov. 1, 1949 

1. A METHOD FOR PREPARING A DICHLOROSTYRENE HAVING ONE CHLORO SUBSTITUENT ORTHO TO THE VINYL GROUP, WHICH METHOD COMPRISES PASSING AT LEAST ONE MEMEBER OF THE GROUP CONSISTING OF 2,3-, 2,4-, AND 2,5-DICHLOROCUMENE THROUGH A DEMETHANATING ZONE MAINTAINED AT A TEMPERATURE BETWEEN 525* AND 750*C. AT A SPACE VELOCITY BETWEEN 5 AND 100 GRAMS OF SAID DICHLOROCUMENE PER 80 MILLILITERS OF CRACKING ZONE PER HOUR, WHEREBY DEMETHANTION OF THE ISOPROPYL GROUP OREDOMINATES TO THE SUBSTANTIAL EXCLUSION OF DEHYDROGENATION, AND RECOVERING A DICHLOROSTYRENE PRODUCT THEREFROM. 